Abstract:

There is a lot of research being done worldwide in harnessing clean energy, like solar energy
and injecting it into existing electricity grids. This project looks at modeling, simulation and
optimization of utility interactive PV power generation in Zimbabwe. Considering the
abundant sunshine in Zimbabwe and decreasing PV prices on the international market, this
can be an option to complement existing power generation from fossil fuels and hydro power
stations.
In this thesis the current state of knowledge of single phase grid connected systems was
looked at.An Integrated inverter which uses a central transformer was selected as the
appropriate system configuration for our environment.
A model of a single phase grid connected Photovoltaic system was developed using
MATLAB and SIMULINK.The complete model is made up of smaller models of the
photovoltaic panel , the inverter and the load .For the photovoltaic model , the algorithm
described by G. Walker [21] was used. For the inverter model, the sinusoidal pulse width
modulation algorithm [B1 was used .Two simulations approaches were looked at: one using
MATLAB and the other using SIMULINK. There was correlation between the two.
The second phase of the project was to develop a laboratory prototype of single phase grid
connected photovoltaic system using inexpensive components which can be sourced locally
or in the region.
The SAB80C535 microcontroller was used to realize all the control functions of the inverter.
Key parameters which were used in the design of the system included inductor size, power
from the photovoltaic panel and the size of the DC capacitor. The inductor size was chosen
based on simulation results and the capacitor size was chosen based on 3% ripple [21].
The results of the developed hardware correlated well with the results of the simulations
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In conclusion the research came up with a cost effective inverter for grid connected
photovoltaic system. This uses a grid synchronization technique which involves a novel
approach of shifting the grid voltage in advance and locking it to the Pulse width modulated
voltage from the inverter resulting in power transfer to the grid. A contribution was made
towards creation of a PV model Block which can be used in SIMULINK environment. The
simulation tool which was developed can be used as a design tool in single phase grid
connected systems using a DC source.